This invention relates generally to seat frames and more specifically to the joining of a headrest guide tube to a tubular seat frame such as for automotive application.
One method of providing support for the seat back of an automotive seat is to provide a frame of metal tubing which runs generally contiguous to the perimeter of the seat. As automotive seats require headrests for passenger safety, provision is required to secure the headrest to the seat frame.
One manner of mounting a headrest is to provide the headrest with two generally parallel downwardly depending mounting posts which are slidable relative to corresponding guide tubes mounted to the seat frame. The headrest guide tubes generally receive an insert which may be a polymeric sleeve to provide smooth motion. A detent means may also be provided which acts between the headrest guide tube and the headrest mounting posts to maintain position of the headrest at a desired height.
Traditionally the headrest guide tubes were secured to the seat frame tube by welding. This proved undesirable principally because of the difficulty in assuring close dimensional tolerances and good alignment in any cost effective mass production process.
More recently, as evidenced by U.S. Pat. No. 5,759,499 to Dudash and U.S. Pat. No. 6,035,516 to Petersen securement of a headrest guide tube to a seat frame tube by forming beads on the headrest guide tube has been introduced. The securement generally involves forming a web by flattening the seat frame tube and punching a hole through the web in the seat frame tube to receive the headrest guide tube. A first radially outwardly extending bead is formed on the tube and the beaded tube is inserted into the hole using the bead to position the headrest guide tube. A second bead is then formed on the headrest guide tube on the opposite side of the flattened seat frame tube to capture the seat frame tube between the two beads.
A significant drawback to the above beading method is the loss in rigidity associated both with flattening of the seat frame tube and the loss of metal removed in punching a hole of significant diameter relative to the amount of material present in the seat frame tube. In an effort to recover some of the lost rigidity Petersen teaches forming upstanding flanges on either side of the flattened area. Nevertheless, the amount of rigidity provided by the flanges is not significant compared to the rigidity of the seat frame tube before punching.
Another drawback to the process of the foregoing patents is the possibility of the headrest guide tube rotating relative to the seat frame tube. This is undesirable as the positional relationship between the headrest guide tube and the seat frame tube should be maintained in order to maintain orientation of the detent means.
It is an object of the present invention to provide a method whereby a headrest guide tube opening may be formed in a seat tube with only minimal removal of metal from the seat frame tube.
A method of forming a transversely extending passage through a tubular seat frame for receiving a headrest guide tube comprises the steps of:
forming first and second diametrically opposed axially aligned openings through said tubing;
(ii) flowing metal from around said first opening through said tube and through said second opening while expanding said first opening to form at least part of an inner wall of said passage;
(iii) flowing metal from around said second opening outwardly from said tube while expanding said second opening to form an outer wall of said passage extending about said inner wall.
A method of securing a headrest guide tube to a tubular seat frame member of ductile metal comprises the steps of:
(i) forming first and second diametrically opposed axially aligned openings through said tubular member;
(ii) flowing metal from around said first opening through said tubular seat frame member and through said second opening while expanding said first opening to initiate a passage extending through said tubular member;
(iii) flowing metal from around said second opening outwardly from said tubular seat frame member while expanding said second opening to receive said metal from around said first opening and form an upstanding wall about said passage, said passage having an entrance adjacent said tubular seat frame member and an exit distal said tubular seat frame member;
(iv) inserting said guide tube through said passage;
(v) deforming said guide tube to form a first detent on said guide tube for limiting displacement of said guide tube in a first direction into said entrance; and
(vi) forming a second detent by deforming at least one of said upstanding wall and said guide tube to, in conjunction with said first detent, fixedly secure said guide tube to said tubular seat frame member.
The forming of the first and second diametrically opposed axially aligned openings may be carried out by punching. A first detent may be a first bead.
The second detent may be a second bead on the guide tube or alternatively, formed by clenching the upstanding wall about the guide tube.
A portion of the upstanding wall may be caused to flow into the guide tube to secure the guide tube against rotational movement relative to the seat frame.
A recess may be formed in the guide tube prior to clenching to receive the portion of the upstanding wall.
The flowing of metal from around the first and second openings may be achieved by placing the tubing in an extruding die-set with a core of the die-set aligned with the first hole and a cavity of the die-set aligned with the second hole. The core may then be urged toward the cavity to cause metal surrounding the first and second holes to flow into the cavity while simultaneously enlarging the first and second holes to form the guide tube passage.
A tubular seat frame member is provided which has a run of ductile metal tubing with at least two headrest guide tube mounting passages extending transversely therethrough. Each of the mounting passages may have an upstanding wall encircling the passage and extending outwardly from one side of the tubular seat frame member. The passage may have a first end proximal the run of tubing and a second end distal the run of tubing.
The upstanding wall may further have nested inner and outer wall members extending respectively from opposite sides of the tubular seat frame member.
The tubular seat frame member may include a respective headrest guide tube extending through each of the passages. Each of the guide tubes may be secured to the seat frame by first locating means at the first end and second locating means at the second end.
The first and second locating means may be respective beads formed in the guide tube.
The first locating means may be a bead formed in the tube and the second locating means may be a clenching of upstanding wall about the headrest guide tube.
The headrest guide tube and the runs of tubing may have inter-engaging projections and recesses formed therein to restrain the guide tube from rotation relative to the run of tubing.
The run of tubing may have a flattened region in the vicinity of the passage.